1. Field of the Invention
The present invention relates to an accessory for an electrical connector and more particularly to a backshell adapter assembly which includes an adapter body formed with anti-rotation teeth, a threaded coupling nut, a retaining ring and a one-piece shuttle with one or more integrally formed spring arms that are adapted to provide an axial biasing force to force proper mating of the anti-rotation teeth on the adapter body relative to corresponding teeth on an electrical connector when the coupling nut is being secured thereto.
2. Description of the Prior Art
Backshell adapter assemblies are known in the art. Such backshell adapter assemblies normally provide a transition from a plurality of electrical conductors to an electrical connector. An example of such backshell adapter assemblies is disclosed in commonly-owned U.S. Pat. No. 5,580,278.
Known backshell adapter assemblies normally include an adapter body, normally tubular in shape, and a coupling nut. In order to secure the coupling nut relative to the adapter body, a retaining ring is normally used. The coupling nut is normally threaded onto an electrical connector. In order to prevent rotation of the backshell adapter assembly relative to the electrical connector, anti-rotation teeth are provided on the adapter body as well as on the electrical connector which interlock and prevent rotation of the coupling nut relative to the electrical connector, for example, as disclosed in commonly-owned U.S. Pat. No. 5,580,278.
If the interlocking teeth on the adapter body and the connector shell properly mate, rotation of the backshell adapter assembly relative to the electrical connector will be prevented. Unfortunately, false mating of the interlocking teeth on the adapter body and the connector shell is known to occur. The false mating can occur when the rotational force of the coupling nut resulting from threading the coupling nut onto the electrical shell causes radial forces on the backshell adapter assembly which causes the backshell adapter assembly to rotate resulting in the interlocking teeth engaging point to point. During such a condition, since the interlocking teeth are hidden from view, an installer may be unaware of the false mating. As such, such a configuration enables the installers to tighten the coupling nut to the desired torque level without being aware of the false mating thus defeating the anti-rotation feature of the backshell adapter assembly possibly resulting in rotation and loosening and even disengagement of the adapter body relative to the connector shell, for example, due to vibration.
Various solutions have been presented in the art to prevent false mating of the interlocking teeth on the backshell adapter assembly with the interlocking teeth on the connector shell. These various solutions generally involve providing an axial force sufficient to overcome any rotational forces that occur during tightening of the coupling nut to force the interlocking teeth into engagement.
One such solution is illustrated in FIGS. 1 and 2. Referring to FIGS. 1 and 2, a known backshell adapter assembly is illustrated and generally identified with the reference numeral 20. The backshell adapter assembly 20 includes an adapter body 21, formed with anti-rotation teeth, aligned in an axial direction and generally identified with the reference numeral 24, a thrust bushing 26, a Bellville washer 28, a coupling nut 30 and a pair of C-clips 27, which are adapted to be received in a retaining groove 29 on the thrust bushing 26, forming a retaining ring. The backshell adapter assembly 20 also includes an anti-decoupling mechanism to prevent the coupling nut 30 from rotating relative to the adapter body 21. The anti-decoupling mechanism includes a plurality of teeth 32 disposed in a radial direction which cooperate with one or more leaf springs 34, 36, disposed in an annular grove 38 in the coupling nut 30. The leaf springs 34, 36 include one or more tabs 40 that are adapted to engage the teeth 32 to prevent rotation of the coupling nut 30 relative to the adapter body 22.
As shown in FIG. 1, the thrust bushing 26 is disposed in an annular groove 42 on the adapter body 21. As discussed above, the C-clips 27 are received in the retention groove 29 on the thrust bushing 26 and form a retaining ring. The retaining ring is adapted to be received in an annular groove 44 on the coupling nut 30 in order to capture the coupling nut 30 relative to the adapter body 22 to prevent movement in an axial direction.
As shown in FIG. 1, the Bellville washer 28 is disposed adjacent the retaining ring 26 in the annular groove 42 on the adapter body 22. In order to prevent false mating of the interlocking teeth 24 on the adapter body 22 with corresponding teeth on the connector shell (not shown), the Bellville washer 28 is used. More particularly, as the coupling nut 30 is threaded onto the connector shell (not shown) by way of the threads 46, the bellville washer 28 exerts an axial force in the direction of the arrow 44 which overcomes any anticipated radial forces which would tend to rotate the adapter body 22 which force the mating teeth 24 on the adapter body 22 into proper mating arrangement with the corresponding mating teeth on the connector shell.
U.S. Pat. No. 5,435,760 provides a similar solution. In particular, a Bellville or wave washer is used to provide an axial force in the direction of the electrical connector to overcome any rotational forces on the adapter body to ensure proper seating on the adapter body and connector shell.
There are several problems with the solutions discussed above. In particular, both solutions utilize a wave or Bellville washer, normally formed from tempered metal. As such, such washers are subject to corrosion and tend to vibrate severely and can damage to softer backshell materials, such as aluminum and high temperature thermoplastic composites. Another problem with the configuration illustrated in ""760 patent is that the wave spring is tightened to a flattened condition to act as a retainer ring to capture the coupling nut which can permanently distort the wave washer causing it to lose its inherent memory.
The backshell adapter assembly 20 illustrated in FIGS. 1 and 2, solves the above-mentioned problem while also providing axial loading without the need to flatten the wave washer and use it as a retaining ring to axially couple the coupling nut to the adapter body. Indeed, as discussed above, the backshell adapter 20 illustrated in FIGS. 1 and 2 utilizes a thrust bushing with an annular groove for receiving one or more C-clips which act as a retaining ring thus obviating the need to use the Bellville washer as a retaining ring.
Although the configuration illustrated in FIGS. 1 and 2 provides an adequate solution to the problems discussed above, the adapter assembly 20 illustrated in FIGS. 1 and 2 include a relatively large number of parts making it relatively expensive to manufacture. Indeed, as discussed above, the prior art backshell adapter assembly 20 includes a two-piece shuttle mechanism which includes a thrust bushing and a Bellville washer. Moreover, the Bellville washer is made of metal and is subject to corrosion and vibration as discussed above. Thus, there is a need for a backshell adapter assembly which prevents false mating of interlocking teeth on the adapter body relative to the connector shelf which is formed with less parts and is less expensive to manufacture.
Briefly, the present invention relates to a backshell adapter assembly which includes an adapter body, a coupling nut, a retaining ring and a one-piece shuttle mechanism. The one-piece shuttle mechanism is formed as a tubular member and is adapted to be received in a retaining groove on the adapter body. In order to facilitate loading of the one-piece shuttle into the retainer groove on the adapter body, the one-piece shuttle is cut along its length to enable the cut ends of the device to be spread apart in order to load the shuttle mechanism into the retaining groove on the adapter body. In an alternate embodiment of the invention, the shuttle is formed with one or more radially extending protrusions formed in the shape of wedges. These protrusions provide a surface to compress the shuttle to enable the shuttle to be loaded into a coupling nut. In the alternate embodiment, a retaining groove is provided in the coupling nut which captures the protrusions when the shuttle returns to its original diameter. Once the protrusions are captured, axial movement of the shuttle with respect to the coupling nut is prevented, thus eliminating the need for a retaining ring. In yet another alternate embodiment of the invention, the adapter body is formed with a pair of annular grooves with a transition surface therebetween forming a recessed groove and a raised platform. In this embodiment, the extending protrusions on the one piece shuttle are forced into the recessed groove as the coupling nut is initially installed. As the coupling nut is further tightened, the protrusions are forced onto the raised platform and are captured by an annular shoulder formed as a mating protrusion on the interior mouth of the coupling nut. In all embodiments, the one piece shuttle mechanism includes a thrust bushing and one or more concentrically formed spring arms that are adapted to provide axial loading in the direction of an electrical connector shell when the backshell adapter assembly is assembled to an electrical connector. In accordance with another feature of the invention, the one-piece shuttle design is amenable to being formed from high temperature composite materials which eliminates the corrosion problem and minimizes damage during various extreme conditions such as extreme vibration conditions to portions of the backshell adapter assembly which are normally formed from aluminum. Another important aspect of the invention is that the one-piece shuttle assembly minimizes the number of parts required and thus significantly reduces the manufacturing costs of such backshell adapter assemblies.